1. Field of the Invention
The present invention relates to a piezoelectric element having high adhesiveness and a film formation method for crystalline ceramic.
2. Description of the Related Art
There are many products where piezoelectric ceramic is applied, such as piezoelectric actuators serving as a mechanical drive source utilizing the inverse piezoelectric phenomenon of piezoelectric ceramic, ceramic filters utilizing resonance, and transducers. In piezoelectric ceramic, a dielectric body having a perovskite crystal structure is used.
For example, piezoelectric actuators are excellent in terms of precision of displacement, generative force and speed of response, and multilayer piezoelectric actuators are used for X-Y tables in semiconductor manufacturing apparatuses, precision processing, printer heads and optical devices etc.
Japanese Laid-Open Patent Publication No. 2002-185285 proposes a method according to which a piezoelectric thin film resonator having excellent adhesiveness to a substrate can be obtained by arranging an electrode film on a substrate via a TiOx (0≦X≦2) film which functions as an adhesive layer, and changing the value of X in sequence in the direction of the film thickness, toward the electrode film. Accordingly, the piezoelectric thin film resonator has a structure where a metal TiOx film is provided between a substrate and an electrode as an adhesive layer.
The metal TiOx film is formed in accordance with any of a vacuum deposition method, a magnetron sputtering method and a laser ablation method, so that the metal TiOx film is changed in sequence in the direction of the film thickness by carrying out heat treatment in an oxygen atmosphere or in normal atmosphere after formation of a metal Ti film.
Japanese Laid-Open Patent Publication No. 5 (1993)-214525 proposes a method for manufacturing a cathode target according to which the outer surface of a target holder in cylindrical form is processed to a rough surface, at least one layer from among layers made of a metal or an alloy having a coefficient of thermal expansion between that of a ceramic layer and that of a target, and layers made of a metal or an alloy having a coefficient of thermal expansion close to that of a ceramic layer is formed as an undercoating, and then a ceramic powder is plasma sprayed so that a ceramic layer is formed, and thus, a film of ceramic can be formed without requiring conventional equipment for manufacturing ceramic, and without a joining process. In this case, the ceramic powder is a powder containing at least one type from among Zr, Ti, Ta, Hf, Mo, W, Nb, Sn, La, In and Cr, and at least one type from among B, Si and O as main components, and the powder is amorphous ceramic.
Japanese Laid-Open Patent Publication No. 5 (1993)-214526 proposes a method to obtain a ceramic powder containing at least one type from among metals M (Zr, Ti, Ta, Hf, Mo, W, Nb, Sn, La, In and Cr) and Si as main components, and containing predetermined ratios of metals M as a total and Si, by using a method for manufacturing a cathode target similar to that of above-mentioned Japanese Laid-Open Patent Publication No. 5 (1993)-214525.
Japanese Laid-Open Patent Publication No. 8 (1996)-157213 proposes a configuration where a metal substrate, a metal layer, a ceramic buffer layer, a crystalline ceramic layer and an oxide superconductor layer are layered in sequence, and the ceramic buffer layer is made up of a lower amorphous ceramic layer and an upper crystalline ceramic layer, in order to obtain an oxide superconductor having excellent orientation and crystallinity.